The present invention relates to high pressure/temperature devices and, more particularly, to apparatus for the synthesis of superhard materials, such as diamond and cubic boron nitride, in which apparatus provision is made for introducing appropriate leads, e.g., the wires of a thermoelement for temperature measurements, into the reaction zone.
A high pressure/temperature apparatus is known (see, for example, U.S. Pat. No. 3,088,170), wherein lead-ins are used as components of a measuring circuit insulated from the heating circuit and are incorporated into the reaction space (vessel) via a pyrophyllite packing (burr).
This prior art apparatus is disadvantageous in that the lead-ins pass through a packing (burr) and this arrangement causes frequent mechanical damage or breakage of thermoelement wires which are affected by marked mechanical loads and undergo significant strains in the zone of the pyrophyllite burr packing. The apparatus suffers from a further drawback of rendering the insulation of the measuring circuit susceptible to damage as a result of packing (burr) material flow, so that an electric contact between the measuring circuit and apparatus elements is likely to occur.